Python编程从入门到实践-第2章

一、字符串：一系列字符，python中用一号括起来的即为字符串，可单可双

"This is a string."
'This is also a string.'

 

#引号灵活性的作用：可在字符串中包含引号和撇号

'I told my friend,"python is my favorite language!"'
"the language 'Python' is named after Monty Python,not the snake."

 

#1.使用方法修改字符串大的小写

name = "ada lovelace"
print(name.title())

name = "ada lovelace"
print(name.upper())

name = "ada lovelace"
print(name.lower())

 

#2.合并（拼接）字符串

first_name = 'ada'
last_name = 'lovelace'
full_name = first_name + ' ' +last_name

print(full_name)

print ("Hello," + full_name.title() + "!")

message = "Hello," + full_name.title() + "!"
print (message)

 

#3.制表符或换行符添加空白
#制表符:\t

print ('python')
print ('\tpython')

 

#换行符：\n

print ('python')
print ('\npython')
print ('Languages:\nPython\nC\nJavaScript')

 

 

 

#同时使用制表符和换行符
print ('Languages:\n\tPython\n\tC\n\tJavaScript')

#4.删除空白:rstrip,lstrip,strip
#rstrip:删除右侧空白

#lstrip:删除左侧空白
#strip:删除两侧空白

favorite_language = 'python '
print (favorite_language)

favorite_language = 'python '
print (favorite_language.rstrip())


favorite_language = 'python '
favorite_language = favorite_language.rstrip()
print (favorite_language)

 

favorite_language = ' python '
print (favorite_language.rstrip())
print (favorite_language.lstrip())
print (favorite_language.strip())

 

二、数字

#数字：
#1.整数：+、-、*、/

print(2+1)
print(3-1)
print(2*3)
print(3/2)
print(2+3*4)
print((2+3)*4)

#2.浮点数：小数

print(0.1+0.1)
print(0.2+0.2)
print(2*0.1)
print(2*0.2)
print(0.2+0.1)
print(3*0.1)

#3.避免类型错误：str()

错误示范：

age = 21
message = "Happy " + age + "rd Birthday!"
print (message)

正确：

age = 21
message = "Happy " + str(age) + "rd Birthday!"
print (message)